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- Hannukainen, Julia D., et al.
(författare)
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Axial anomaly generation by domain wall motion in Weyl semimetals
- 2020
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 102:24
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Tidskriftsartikel (refereegranskat)abstract
- A space-time dependent node separation in Weyl semimetals acts as an axial vector field. Coupled with domain wall motion in magnetic Weyl semimetals, this induces axial electric and magnetic fields localized at the domain wall. We show how these fields can activate the axial (chiral) anomaly and provide a direct experimental signature of it. Specifically, a domain wall provides a spatially dependent Weyl node separation and an axial magnetic field B-5, and domain wall movement, driven by an external magnetic field, gives the Weyl node separation a time dependence, inducing an axial electric field E-5. At magnetic fields beyond the Walker breakdown, E-5. B-5 becomes nonzero and activates the axial anomaly that induces a finite axial charge density-imbalance in the number of left- and right-handed fermions-moving with the domain wall. This axial density in turn produces, via the chiral magnetic effect, an oscillating current flowing along the domain wall plane, resulting in a characteristic radiation of electromagnetic waves emanating from the domain wall. A detection of this radiation would constitute a direct measurement of the axial anomaly induced by axial electromagnetic fields.
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| 2. |
- Hannukainen, Julia D., et al.
(författare)
-
Electric manipulation of domain walls in magnetic Weyl semimetals via the axial anomaly
- 2021
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Ingår i: SciPost Physics. - : Stichting SciPost. - 2542-4653. ; 10:5
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Tidskriftsartikel (refereegranskat)abstract
- We show how the axial (chiral) anomaly induces a spin torque on the magnetization in magnetic Weyl semimetals. The anomaly produces an imbalance in left- and right-anded chirality carriers when non-orthogonal electric and magnetic fields are applied. Such imbalance generates a spin density which exerts a torque on the magnetization, the strength of which can be controlled by the intensity of the applied electric field. We show how this results in an electric control of the chirality of domain walls, as well as in an improvement of the domain wall dynamics, by delaying the onset of the Walker breakdown. The measurement of the electric field mediated changes in the domain wall chirality would constitute a direct proof of the axial anomaly. Additionally, we show how quantum fluctuations of electronic Fermi arc states bound to the domain wall naturally induce an effective magnetic anisotropy, allowing for high domain wall velocities even if the intrinsic anisotropy of the magnetic Weyl semimetal is small.
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